Monday, June 27, 2011

David Linden’s book The Compass of Pleasure describes the latest neuroscience research on the medial forebrain pleasure circuit (interesting, these computer metaphors for brain anatomy).

One fascinating entropy-related finding is that the pleasure circuit activates with less intensity after each subsequent stimulant dose. A thirsty Cro-Magnon man roaming through the Sahara comes upon a stream and takes a long drink. The sandy water is the best thing he has ever tasted. A thunderstorm of pleasure is flashing inside of his head. He takes another drink. The cold water runs down his throat and seems to spread its coolness throughout his entire body. He takes a third drink. The inside of his mouth is saturated, no longer parched. But after the fourth and fifth slurp, he begins to taste the imperfections. He feels the sand in his teeth and the back of his throat. The water doesn’t seem as cold and refreshing. It doesn’t taste quite so watery. He takes one last drink for good measure and moves on.

A modern corollary is the fancy New York restaurant that only serves small steaks (heresy most everywhere else in America) because, as the restaurateurs say—as if facts mattered when the size of a man’s steak is at question—after the twelfth bite the pallet is so deadened as to render the remaining bites useless. What we call pallet is nothing but the pleasure circuit’s sensors in the mouth.

What fascinates me is that the concept of entropy is imbedded deep in one of the most fundamental processes for how we interpret reality. This must account for the bedrock and universal human psychological/emotional concept of carpe diem, stopping to smell the roses, and the joys of simple pleasures. While the pleasure circuit itself ensured that our ancestors stopped to take that drink and was quenched by it, that they lusted for sex, that they relished the taste of fat and protein and sugar. But the diminishing pleasure return may have taught them to be self-reflective about those brief moments of heightened experience. The loss of pleasure may have started those early humans to think about their emotions, and—a small leap here—to think about their thoughts. This might have been one key to the evolution of human consciousness, the brain in all its self-aware glory.

A thermodynamics question: why did the pleasure circuit have to work this way? Why not have the fiftieth bite of chocolate butter cream cake taste as exquisite as the first? Apart from the answer that the Universe just doesn’t work that way, which we all feel intuitively (what would Heaven be for?), I hazard two interpretations. The pleasure circuit is beholden to the same laws of thermodynamics as anything else. It requires energy to produce that initial burst of pleasure, and it cannot be expected to maintain that any more than you can do an infinite amount of pushups.

A second idea: in order to function in the world, we have to be able to move on, especially from things that provide pleasure. We must learn to take in all substances and experiences in moderation. The fact that pleasure (happiness) doesn’t last, and that shoving that fiftieth forkful into our mouths actually leaves us unsatisfied and unhappy, teaches us not only the necessity of moderation, but the pleasure of moderation. And as has been catalogued on this blog already, moderation is what slows the degradation of energy in our bodies, our environments, or families, our societies.

To write this blog is to realize over and again this fundamental, universal, spookily pre-ancient truth.

Much of the book is also about addiction. Listen to a great interview with Linden on Fresh Air: